Properties of Polyaluminum Chloride and Its Application in Papermaking Wet

[Chinese aluminum industry] Aluminum sulfate has a long history as a precipitant for rosin sizing, but it is only suitable for acidic conditions. With the rapid development of the paper industry, neutral sizing has increasingly shown its unique advantages, and has a tendency to replace acidic sizing.

The neutral sizing system consisting of aluminum sulphate instead of aluminum sulphate and anion disperse rosin gum makes full use of inexpensive rosin to achieve neutral sizing without having to make more changes to the original system. It has many advantages such as practicality and low sizing cost, and it is a sizing method suitable for China's national conditions. Taking the neutral sizing system consisting of polyaluminum chloride and anion disperse rosin gum as the center, the following aspects were studied: First, the characteristics of polyaluminum chloride and its influencing factors were studied. The results show that the hydrolysis and polymerization of polyaluminum chloride are affected by many factors such as the degree of alkalization, the total aluminum concentration, and the preparation methods, which are mainly reflected in the changes in the composition of Ala, Alb and Alc in polyaluminum chloride. In addition, some environmental factors will also affect the change of its morphological composition. For example, when the polyaluminum chloride is diluted in water, different dilution stages and dilution times have different conversion effects between its various polymer form components; with the pH value Gradually increased or prolonged ripening time, the polymerization forms of the polyaluminum chloride all have a higher degree of polymerization. Second, the specific application of polyaluminum chloride in the wet end of papermaking was studied and compared with aluminum sulfate from various angles. The experimental results show that the sizing effect is different with different polyaluminum chloride sizing precipitators; when the amount of disperse rosin gum is 1.0%, the amount of polyaluminum chloride is 0.8% (calculated as Al2O3%), the sizing effect It is preferable that some cationic wetting additives, such as amphoteric starch, cationic polyacrylamide, and cationic wet strength PAE, can improve the effect of neutral sizing to varying degrees, and that the synergistic effect of amphoteric starch and cationic polyacrylamide can be further enhanced. Improve the sizing effect; the pH value of the slurry has a greater influence on the rosin sizing, and the sizing with polyaluminum chloride and anionic disperse rosin gum can achieve a pH of 7.5; the addition of the filler has a greater effect on the sizing effect. The effect of heavy calcium carbonate is even more pronounced with large influences; in addition, the sizing effect is also affected by many other factors such as the type of slurry, pressing pressure, and drying temperature.

The polyaluminum chloride with different concentration and degree of alkalization has no obvious difference in retention and drainage aid. Polyaluminum chloride, amphoteric starch and cationic polyacrylamide can increase the retention rate of bleached wheat straw pulp and paper in different degrees. The water filtration performance, and the synergistic effect of polyaluminum chloride with other positively charged retention aids, can significantly increase the retention of the bleached wheat straw pulp stock; in addition, the stirring speed has a one-time retention rate for the bleached wheat straw pulp. Obvious effect, with the increase of stirring speed, the retention effect of polyaluminum chloride is significantly reduced, when used in combination with amphoteric starch or cationic polyacrylamide, it can effectively improve its shear resistance; contact time for polychlorinated The effect of aluminum retention is less, while the effect of amphoteric starch and cationic polyacrylamide is relatively large; several additives have a good retention effect in the neutral range, and polyaluminum chloride and bisexual The combined use of starch or cationic polyacrylamide obviously achieves a better retention effect under medium and alkaline conditions.